Chromosome damage caused by exposure of humans to pesticides and herbicides is now well documented. However, there are only a few cytogenetic studies of chemically exposed populations that have shown to actually constitute a human health hazard. Therefore, we plan to undertake a cytogenetic investigation of two independently exposed populations in North Alabama; one with accidental chronic DDT exposure and high serum DDT levels and another with heavy pesticide. Sister chromatid exchanges (SCE) and chromosomal aberrations will be measured as indicators of damage. Blood samples will be obtained from exposed individuals and their matched controls (matched for sex, age, medical history and lifestyle). Laboratory tests will examine SCEs and will be done of individuals with differing levels of exposure. The results will be analyzed for the relationship between exposure and health effects, and also indicate the dose-response relationship.